Automatic control for centrifugal casting machines



Oct. 29, 1929 G. c. PFEFFER AUTOMATIC CONTROL FOR CENTRIFUGAL CASTING MACHINES 5 Sheets-Sheet 1 Filed June 5 1928 r7 9 W W H Q whwfi m0. m e m1 w I! W. EN NNRN Oct. 29, 1929. G. c. 'PFEFFER 1,733,820

AUTOMATIC CONTROL FOR CENTRIFUGAL CASTING MACHINES I Filed June 5, 1928 5 Sheets-Sheet 2 A If.

v WITNESSES I N VEN TOR:

George (I iffijfi;

d M I d I ATTORNES.

1929- G. c. PFEFFER 1,733,820 AUTOMATIC CONTROL FOR CENTRIFUGAL CASTING MACHINES Filed June 5, 192 8 3 Sheets-Sheet 5 1/ FIG. 12". 1

INVENTOR: Gaol-ye (Z Pfqf/er,

W1 TNESSES I l I I ATTORNEYS.

Patented Oct. 29, 1929 we, at

UNITED STATES PATENT orrioa.

GEORGE c. PFErFER, or FLORENCE crownsmr, nunmneronfcoonrizynnw JERSEY,

ASSIGNOR To WALTER WOOD, or PHILADELPHIA, PENNSYLVANIA AUTOMATIC GO NTROL FOR GENTRIFUG-AL CASTING MACHINES Application filed June 5,

My invention relates to electrical apparatus for controlling the different speeds at which the mold of a centrifugal casting machine is rotated in carrying out the various steps in making a casting by the centrifugal process, and has particular reference to mech nism for automatically accelerating the prime mover to eflect the desired changes in speed at the proper times.

In the art of centrifugally casting hollow metal bodies, a metal flask lined with molding sand is placed horizontally in the casting machine, and the mold is caused to rotate at a relatively low speed, say 50 R. P. M. The

- flask is then elevated to full inclination and subsequently depressed graduall while molten iron is poured into 1t, distri uting itself longitudinally along the bottom of the mold. When the flask has returned to horizontal position, the spinning velocity of the mold is at once greatly-increased. There is a resulting development of centrifugal forces which takes place so rapidly that to all practical purposes it appears to be instantaneous. This .25 force casts the molten metal onto the cylindrical wall of the sand-lined mold, and every part of the casting is formed at the same moment.

Heretofore it has been the common practice in this art to regulate the speed of the motor which drives the flask by a controller, the latter being manually o ated, or, automatically operated by mechanlcal means which are actuated by themovement of the flask carriage from one position to another. With manual control, twooperators are needed, one to manipulate the controls which operate the tilting mechanism, and another to manipulate the motor speed controls. On the other hand, where mechanical means are employed to automatically operate the motor controller, the machinery is necessarily bulky, a large number of moving parts are required, and the apparatus. does not possess the durabllity which is desirable in a machine which is continuously in operation.

With the foregoing in view, my invention provides electrical means for automatically accelerating the motor speed as the flask is lowered from the tilted'position to the hori- 1928. Serial No. 282,966.

zontal, and additional mechanism to enable the operator to make rapid changes from one predetermined speed to another. With the use of my invention, an unskilled operator can by manipulation of a series of centrally located push buttons perform all the steps necessary to carry out the castingoperation. Supplementing. these advantages are those derived from the provision of additional emergency controls which enable the operator to depart from the normal sequence of operations and to eflect any desired change in the speed of the motor.

The various features of novelty which characterize my invention are pointed out with particularity in the detailed description which follows. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings, in which I have illustrated and described a preferred embodiment of the invention.

, Of the drawings:

Fig. I is a diagrammatic front View of a centrifugal casting machine embodying my 1nvention. Q

Fig. II is an enlarged view of a door switch which is. closed when the machine is in filling position.

Fig. III is an enlarged view of a second door switch which is closed when the machine is in normal or spinning position.

Fig. IV is 'an electrical diagram showing the operation of the motor controls. a

Fig. V is a schematic diagram-illustrating the operation of the various contactors, shown in Fig. IV; and,

4. The motor 1 and a hood 5, which houses the flask 3, are mounted on a tiltable carriage 6, which is pivoted at 7, and which is' nclmed loo from the horizontal position by means of a hydraulic ram 8, and depressed by gravity. At the rear of the machine there is a control panel, comprehensively designated by the numeral' 9, carrying the push buttons 10, 11, 12 and 13, the shunt field rheostat 33, the slowdown rheostat 32 and the armature shunt rheostat 34. On the base of the carriage 6, near its fulcrum point 7, there is a bracket 16 for operating the door switch 17 which is conveniently located on a floor beam 18. The doorswitch 17 is of a common type, having a spring actuated knob 19, normally retained in downward position, but which is carried upward by the bracket 16 when the carriage 6 is inclined to its maximum elevation. In the horizontal or spinning position, the switch 17is held open by its spring, whereas in the inclined or filling position the switch 17 is closed by its contact with the bracket 16.

On the floor beam 18 there is an additional door switch 20, near the charging end of the machine, which is operated by a hinged lever 21. It likewise carries a spring actuated knob 22 which is normally held in the downward position by the weight 23, but which upon the elevation of the carriage 6 and the consequent release of the weight 23 is caused to rise. The weight 23 is preferably suspended from a drum 24 on the tilting carriage 6 by a wire 25 which passes through the lever 21 and carries a stop 26 to co-operate with the lever when the carriage is elevated or depressed. The drum24 enables an adjustment of the length of slack wire when the carriage 6 is I horizontal, thus governing the position at which the switch 20 will operate. In the horizontal position the switch 20 is closed. Upon the raising of the carriage 6 the wire 25 becomes taut, the weight 23 is released from the lever 21, and the switch 20 springs open.

The various contactors, switches and rheostats used for controlling the speed of the motor 1 are diagrammatically illustrated in Fig. IV. At the top of the drawing are shown the door switches 17 and 20, which are opened and closed by the movement of the tilting carriage 6 as hereinbefore described, together with the stop button 10, the start slow button 11, the slow down button 12, and the fast button 13. Below the control switches there is a contactor panel, comprehensively designated by the numeral 27, on which'are mounted the main line contactor M, the armature shunt contactor AS, the fast-1 contactor F, the shunt field relay FR, and the time relay TR. Beneath the contactor panel 27, the motor armature A is shown with its shunt field 30 and series field 31. Two rheostats 32, 33 control the resistance in the shunt field 30 and a third rheostat 34 controls the resistance in the armature shunt circuit.

The various paths which the current takes under different operating conditions are more matic diagram shown in Fig. V, in which the main line conductors are represented by L and L In starting, the tilting carriage is in horizontal position, and consequently the door switch 20 is closed and the door switch 17 is .open. The closing of the main line switch 35, preparatory to the spinning of the centrifugal casting machine, causes current to flow from L through coil FR and then to divide, one path being through the normally closed contact TR of the relay TR and the other through the normally closed contact F of thefast contactor F, to the line L Thus coil FR of the shunt field relay FR is energized and its contacts FR and FR are closed, so that current may pass from line L through the branch line f and the shunt field 30 to the branch line f and thence, through contact FR and normally closed contact TR to line L Accordingly the rheostats 32 and 33 are short circuited, allowing the motor 1 to have full field strength.

The machine is now ready for operation. The operator presses the start slow button 11, and then begins to elevate the carriage 6 to inclined position preparatory to charging the flask 5. The closing of the start slow button 11 permits current to pass from L through the start slow switch 11 to the stop switch 10, which is normally closed, and then through the line m to coil M, and ultimately to line L thus energizing coil M of the main line contactor M, and causing its several contacts M and M to close. The closure of contact M permits current to pass from line L through the contact M to line a, thence through the armature A and line a to the series field 31, and thence through resistors R R R and R to line L A portion of the current in this circuit is shunted around the armature A and passes through the branch line y, the contact AS and the rheostat 34. At this point, there is full resistance in the series field, no resistance in the shunt field, and a variable resistance in the armature shunt circuit. Accordingly, the motor is permitted to run at a very low speed, say 50 R. P. M., this speed, however, being capable of regulation by means of the rheostat 34.

When the carriage 6 has reached its highest position, door switch 17 has closed, and door switch 20 has opened. The closing of door switch 17 allows current to pass from L" through contact M to the branch line b, thence through switch 17, the normally closed slow down button 12 and the coil F to line L Thus the coil F is energized, causing meaaao After the flask or mold 5 has been charged, the carriage is lowered to horizontal position. Door switch 17 opens immediately, but there is no affect upon the circuit because contactor F continues to be energized by current flowing from L through the 'contact M the branch line b, the contact F, the, slow down switch 12, and the coil F to the line L Just before the carriage 6 reaches the horizontal position, and at a predetermined point dependent upon the adjustment of the drum 24, the 'door switch 20 closes. This closes a circuit from L throu h the contact M the line b and the contact 3 to the coil AS and thence through the switch 20, the contacts F and FR to line IF. Thus coil AS of the armature shunt contactor AS is energized producing three different eflects: First, the normally closed contact A8 is opened, permitting full current to pass through the armature A; secondly, contact AS is closed so that the coil TB of the time relay TR is energized and resistors R R R and R in the armature and series field 31 are short circuited; and, thirdly, contact TR which is normally closed, is opened so that the coil FR is no longer energized, and the contacts FR and FR are opened, thereby inserting the resistance of the field rheostat 33 in series with the shunt field 30. Accordingly, at this point there is no resistance in the armature A and series field 31, there is full current through the armature A, and there is a variable resistance 33 in the shunt field 30. This condition causes a very rapid accelerationof the motor, its speed being determined by the setting of the rheostat 33 and preferabl attaining about 1200 R. P. M. This very high speed centrifugally disperses the molten metal in the flask 5 so that it forms a hollow cylindrical body on the wall of the sand-lined mold. The. pipe having formed and havin begun to cool, the speed of the motor may be reduced. For this purose the slow down button 12 is pressed y the operator, causing the circuit through line 03 and coil F to open, which in turn closes contact F and again energizes the coil FR. The resulting operation of contactor F R closes contact FR? and inserts the slow down rheostat 32 in parallel with the field rheostat 33, thus reducing the speed by a predetermined amount dependent upon the setting of the slow down rheostat. Therheostat 32 is preferably set so that a slow down speed of about 900 'R. P. M. is attained.

If, at any time while the carriage 6 is in horizontal position and the switch 17 is of necessity open, the operator desires to obtain full motor speed, he has simply to press the fast button 13 to obtain this result. The closure of the fast switch short circuits the door switch 17, and permits current to pass through the coil F and hence to operate the fast contactor F, causing the same effect as the automatic acceleration which is had when the carriage returns from inclined to spinning position. The fast button eliminates the necessity of going through the entire sequence of operations, and is particularly useful when testing the apparatus or when it is desirable, in the course of normal operation, to slow down and to speed up again.

To stop the machine at any time, regardless of the position of thevarious contactors the stoplbutton 10 is employed. This is a normally closed switch which when opened breaks the circuit to the coil M of the main line contactor M, and hence opens contact M which in turn breaks the circuit from the main line L to the armature A and stops the motor 1.

In Fig. VI of the drawings, I have shown a modification of my invention, illustrating an alternative method of reducing the armature voltage for running the motor 1 at very low speeds. For this'purpose I employ a separate low voltage generator G, and I add .to the armature shunt contactor AS an additional contact AS, which is normally open,

but which closes when the coil AS is energized. With this arrangement, the operation is substantially similar to that described. When the start slow button 11 is pressed operating the main line contactor M, the contact M is closed, and current from the generator G passes through the normally closed contact AS and the contact M to the armature A;'thence through the rheostat 34 back to the generator G. The motor 1 is caused to run at .a very low speed which can be varied by the rheostat 34. When the door switch 20 closes operating contactor AS, the contact AS is opened breaking the low voltage circuit from the 1 generator G, and the contact AS is closed, allowing current from the line L to pass through the armature A to the line L It will be apparent that the same changesin speed may be acquired with the modified device as with the apparatus reviously described, and that the use of a ow voltage generator makes it posslble to run the motor 1 at speeds far below its normal slow speed. While the generator G is illustratedas a separate unit, it is preferably a part of a motor-generator set, the motor of which derives its current from lines L and L and which is set in motion by the closing of the main switch 35. 1

It will be readily apparent that the position of the various rheostats for obtaining the desired changes in speed in the course of making a casting may be determined by experimentation, and once determined, the rheostats need not ordinarily be tampered with, for the operator can,by the use of the control buttons, perform all the necessary operations. The use of control buttons, rather than other manually operated electrical devices efiects a great saving intime and enables an unskilled operator to tend the casting machine with ease. Furthermore, the door switches 17 and 20, which are automati cally operated by the movement of the carriage, not'only relieve the operator at a time when he is engaged with the tilting controls, butalso act as safety devices as they prevent any fast running of the machine while the mold is being charged, and thus save many castings from defective manufacture.

WhileI h ve described my invention with some particu arity, I desire it to be understood that changes may be made in the form of the apparatus disclosed without departs ing from the spirit of my inventionfthat electrical means, other than those'specifically described for regulating the motor speed, can be substituted with equal effectiveness, as will be apparent to those skilled in the art; and that certain features of the invention may sometimes be used with advantage without a corresponding use of othervfe atures.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a centrifugal casting machine comprising a tiltable rotary mold, an electric motor for rotating the same, and means for elevating and depressing said mold; electric means for causing the motor to run at a comparatively low speed, supplemental means to rapidly accelerate the speed of the motor, a switch actuated by the elevation of the mold to prepare said supplemental means. for operation, and a second switch actuated by the depression of the mold to operate said supplemental means whereby the mere elevation and depression of the mold causes automatic acceleration of the motor.

2. In a centrifugal casting machine comprising a tiltable rotary mold, an electric motor for driving the mold, and means for elevating and depressing themold; a series of electric contactors and resistors co-operatlng with the field circuits of said motor to cause it to normally run at a comparatively low speed, a pair of switches, one actuated by the elevation of the mold and the other actuated by its depression, and supplemental electric means for causing "rapid acceleration of the motor, said means co-operating with the switches aforesaid so that the elevation and subsequent depression of the mold automatically accelerates the motor.

In a centrifugal casting machine comprising a tiltable rotary mold normally retamed in horizontal position, an electric motor for driving the mold, and means for elevating and depresslng said mold; an electric circuit for causing the motor to run at a comparatively low speed when themold is either in speed when the mold is either in horizontal or inclined position, a'switch actuated by the elevation of the mold, a second switch actuated by the depression of the mold, supplemental electrical means for causing rapid acceleration of the motor, said means belng set in operation by the successive operation of the switches aforesaid, and means for short circuiting the first mentioned switch whereby the motor speed may be accelerated without the mold being tilted.

5. In combination with a centrifugal casting machine comprising a tiltable rotary mold, a motor for rotating the same, and means for elevating and depressing said mold; a switch operated by the depression of the mold, electrical means co-operating with the switch aforesaid to automatically accelerate the speed of the motor when the switch is operated, additional electrical means for causing the motor to run at a predetermined speed slower than the normal accelerated speed, and a push button control for setting said latter means in operation.

6. In combination with a centrifugal casting machine comprising a tiltable rotary mold, a compound motor for rotating the same, and means for elevatin and depressing said mold; a switch operate by the depresly accelerated speed.

7. In combination w1th a centrifugal casting machine comprising a tiltable rotary mold, a motor for rotating the mold, and means for elevating and depressing the mold; a switch actuated by the depression of the mold from inclined position, an electric circuit for causing the motor to run at a very low predetermined speed, a second electric circuit co-operating with said switch for causing the motor to automatically accelerate to a predetermined speed, a third electric circuit for causing the motor to slow down to a predetermined speed greater than low speed and less than accelerated speed, and a series of push button controls for operating each of said circuits.

8. In combination with a centrifugal cast- I means for elevating and depressing the mold;

a switch actuated by the depression of the mold from inclined position, a low voltage generator for causing the motor to runv at a.

very low predetermined. speed, a high voltage line leadlng to said motor, and electrical means cooperatingwiththe switch aforesaid to, cut out the low voltage generator and to cut in the .high voltage line when the switch is actuated; whereby thespeed of the motor is greatly accelerated; vp In testimony whereof, I' have hereunto signed my name at Florence, New Jersey this 31st day of May, 1928.

. GEORGE PFEFFER. 

